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What Do Goats Really Like To Eat?

Introduction

All my life I have been
told or have read about goats supposedly eating anything and every thing.
Even some Department of Agriculture documents have claimed that goats
have a "catholic" taste, meaning that they have a universal, liberal
approach to what they eat. We all see cartoons of goats "eating"
clothes hanging from the clothes line, or munching on tins and other
rubbish. So what is the truth about goat diets?

This article discusses
behavioural studies of goat diet selection, nutritional studies of goat
diets and refers to scientific studies of goat diets in Australia. But
first I must refer to a very old story.

What does the story
about the Three Billy Goats Gruff teach us?

I have always enjoyed
reading the story of the Three Billy Goats Gruff to my daughters. In
every one of the 30 or so versions that I have read the goats are prepared
to risk death to EAT FRESH GREEN GRASS.

Indeed in almost every
scientific study conducted on the grazing preferences of goats, when
fresh green grass is available, the goats have eaten more than 50% of
their diet as green grass. In Victoria, during spring, my studies showed
that Angora and cashmere goats consumed more than 80% of their diet
as green grass. The writers of the Billy Goat Gruff story had really
observed what goats ate.

Is green grass good
for goats? Yes, green grass is the generally the most nutritive
food available for goats and it is the cheapest food. During spring
the green pasture is usually about 80% digestible and has a crude protein
content of 20%. Most of the fibrous parts of the pasture are still quite
digestible by the goat. As a result goats can eat lots of the spring
pasture and because the pasture is has a very high nutritional value
they can grow quickly. The fastest growth rates recorded for weaned
goats in southern Australia are from goats grazing spring pasture. The
important exceptions to this are when pastures have trace mineral levels
that are less than the needs of goats. This usually occurs on
soils that have low trace mineral levels.

So why don't goats
only eat green grass? Sometimes there is no green grass, or it is
too short for goats to easily graze. Some species of grass have low
nutritive value even when they are green (like tussocks or some tropical
grasses). Sometimes the goats cannot help eating other material, like
dead grass mixed with the growing green grass leaves. Sometimes goats
prefer to eat other more easily grazed plants. Goats tend to select
away from growing clovers but there is no evidence that clovers are
harmful to goats. In my studies, when grazing pressure was increased,
goats ate clover without harm and from late spring, when the clover
flowered and matured, goats ate dry clover pasture.

The behaviour of goats
is discussed further in the following section.

The dietary behaviour of goats

In Australia, farmers
are familiar with the grazing behaviour of sheep. As a generalisation
goats have evolved and adapted to live in different environments or
to use the environment differently to the sheep we farm in Australia.
So how do goats choose their diet? The explanation that I like uses
three aspects of the behaviour of grazing animals to classify how they
choose their diets. These aspects of behaviour are selectivity, degree
of browsing/grazing and flexibility.

Selectivity
Generally goats are more selective compared to sheep. Goats have
evolved to adapt to a wider variety of plants including very prickly
plants and some bitter tasting plants which sheep avoid.

Goats have also evolved
a narrower muzzle compared to sheep and this allows them to nibble the
nutritious young shoots and leaves of prickly bushes and to strip the
bark from some stems. In this way goats are able to survive better
in arid areas where sheep are not as well adapted. The narrower muzzle
may place goats at a disadvantage when only very short pasture is available.
By comparison cattle are less selective partly because they have a wide
mouth.

But goats eat weeds,
surely this is not a good nutritional strategy? Yes goats do eat some
weeds but the nutritional value of many weeds is very high. My
studies of the nutritional value of thistles and blackberries (Table
1), for example, have shown that the nutritional value of these "weeds"
can be as high or higher than the nutritional value of pasture.
In almost all cases the goats selected the most digestible part,
the fraction with the highest digestible energy.

Table 1. The
nutritive value of various parts of the blackberry plant eaten or avoided
by goats

Plant
part

Eaten by Goats

Dry matter digestibility%

Metabolisable energy MJ/kg DM

Blackberry
leaves Blackberry leaves

Yes

70

10.5

Blackberry
new stems

Yes

73

11.0

Blackberry old stems

No

51

7.5

Blackberry
dead stems

No

45

6.5

Degree of grazing/browsing
Browsing means eating the leaves, shoots and twigs of shrubs and trees.
Goats have special ecological adaptations for browsing such as a split
upper lip, narrower muzzle, longer legs for climbing, different tolerance
to plant chemicals, and the documented ability to travel further each
day than sheep in search of feed.

However it is not correct
to describe goats as browsing animals and sheep as grazers as this is
a misleading description of goats. Browsing is a better description
for the behaviour of giraffe, koalas and some antelopes. Goats are best
described as mixed feeders. Goats tend to browse more than sheep
if the opportunity exists for browsing. Goats can be kept on grazed
pastures without trouble, as I have done for over 20 years.

In my studies, when goats
and sheep were grazed together on annual pastures, at low stocking
rates the species showed different selectiveness, but at very high
grazing pressures when the pasture was short and in very
limited supply the sheep always out competed the goats.
Studies in environments where there is plenty of browse have shown that
increasing the stocking rate of goats usually leads to a reduced intake
of browse as the more palatable plants are eaten.

Flexibility
Goats are far more flexible in their feeding habits than sheep and cattle.
Goats can change their preferences quite quickly. For example
goats may avoid a growing plant for some months but will then eat the
plant when it begins to flower. These flexible habits apply to
both selectivity and grazing/browsing. Goats can eat with high
or low selectivity on browse plants and with high selectivity on pasture,
very flexible!

To be flexible means
that goats must be inquisitive. This results in goats sampling "interesting"
things (and this is where the washing and cans come into the stories).
Sometimes this sampling of new things leads to death when they eat poisonous
plants.

Do goats eat everything?
NO GOATS DON'T EAT EVERYTHING. Their ability to be selective,
to browse and to be flexible has enabled goats to survive in many environments.

But goats need roughage
don't they?

Well this question can
be very tricky to answer as everyone has a different impression of roughage.
The Dictionary defines roughage as follows:

Rough or coarse material

the coarser kinds or parts
of fodder or food, of less nutritive value, especially those which assist
digestion, as distinguished from those affording more concentrated nutrient.

Most Australians know
of the need for roughage or fibre in human diets. Human diets
in Australia are largely based on cereals, meats, fruit and vegetables,
and dairy products with the roughage mainly coming from vegetables,
fruit and some whole grains. In animal science, roughage diets
are composed of forage or herbage. Concentrate diets are composed
of whole or processed grains with a limited amount of roughage.
Generally, forage diets have higher levels of fibre and lignin, and
lower energy concentrations than concentrate diets.

There are many exceptions
to these general statements and the issues can be clouded if you read
a European or American book because the nutritive value of herbages
and "concentrates" varies depending on plant species, season
and the material used in commercial "concentrate" mixes.
There are a number of points that I wish to discuss.

To say that goats
need roughage when they are grazing pasture is double speak.
Pasture is roughage. The fastest growth rates, reported in Australia
for weaned goats, are from goats grazing spring pasture. Fast
growing spring pastures in Australia usually have metabolizable energy
concentrations greater than or equal to that found in high energy concentrate
diets (such as wheat or barley diets).

Research has shown
that goats are generally superior to sheep in digesting feeds with digestibility
between 50 and 60% and that goats have an advantage in digesting the
fibre component of the diet. While these findings show goats utilise
feeds of low digestibility better than sheep it certainly
does not mean that the production of goats increases as the quality
of grazing or roughage decreases. As feed quality falls the
performance of sheep and goats falls. Both species lose liveweight
and are less productive on high roughage diets which have low metabolizable
energy concentrations. For example the fastest rates of liveweight
loss reported for goats are from goats grazing dead summer pasture.
The variation in nutritive value of roughages is enormous (from excellent
to very poor).

Roughage as defined
by the Dictionary means "the less nutritive parts". These
are the "parts" which goats usually select against.
I often ask myself how rough is rough?

How do we can obtain
healthy goats with high levels of production when they are fed concentrate
diets? There is increasing evidence that fibre goats have a higher requirement
for roughage, in order to maximise their food intake, compared to Merino
sheep. The results of several experiments in Australia have shown
that when goats were fed concentrate diets the maximum food intake occurred
when between 13% and 34% of the total intake was chopped hay. This appears
different to work with sheep where whole wheat based diets fed with
straw suggested the roughage requirement of the young sheep did not
exceed 2% of the diet. In most of Australia
it is clear that productivity of goats is maximised when goats are fed
forage diets of high digestibility, which enable high levels of energy
intake and contain sufficient nitrogen and trace minerals. Such diets
enable goats to grow and lactate at high levels.

CONCLUSIONS

Goats are animals that
are flexible and selective feeders. Goats have evolved with a greater
ability to browse and to digest lower quality herbage than sheep.
In southern Australia, when offered fresh green pasture, goats will
tend to consume the most highly digestible grasses in preference to
clovers and other shorter plants. There is no evidence that clovers
harm goats. If fed on rations mainly composed of cereal grains, maximum
feed intake is obtained if about one third of the diet is forage based.
The selective, flexible and browsing nature of goats enables them to
consume very nutritious food from many plants regarded as weeds. Goats
are best described as mixed feeders.